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We thank Dr Grant for her continued interest in our study. The Royal College of General Practitioners’ (RCGP) Oral Contraception Study has prospectively followed up women forward in time, with information about oral contraceptive (OC) exposure collected often many years before the diagnosis of cancer. Follow-up was initially via 6-monthly general practitioner (GP) reports of any hormones prescribed (including hormone therapy [HT] in later years), all new episodes of illness, surgery, and deaths. In the mid-1970s we flagged women still under GP observation at the National Health Service (NHS) Central Registries for subsequent notification of cancers and/or deaths even after detailed GP follow-up ceased. Women frequently changed their OC status (eg, never users became current users, current users became former users, and former users became current users). To allow for this dynamic situation appropriately we analyzed our data using person-time. Thus, for each month that a woman was under GP/NHS Central Registry observation we determined her OC status, to allocate to the correct OC group denominator (time at risk of cancer) and numerator (cancer) information. As we reported, we stopped follow-up of a small number of women when uncertainty arose about OC status.1Iversen L. Sivasubramaniam S. Lee A.J. Fielding S. Hannaford P.C. Lifetime cancer risk and combined oral contraceptives: the Royal College of General Practitioners’ Oral Contraception Study.Am J Obstet Gynecol. 2017; 216: 580.e1-580.e9Abstract Full Text Full Text PDF Scopus (145) Google Scholar When interpreting cohort data it is important not to look superficially at total number of events–the doubling of cancer numbers in the ever vs never user group (4661/2341 = 1.99) occurred during more than double the risk time (884,895/388,505 woman-years = 2.27). We did not adjust for hysterectomy or HT because we did not have this information after women left GP observation. Most women had a hysterectomy for nonmalignant reasons. Among women who remained under GP observation in 1996, 18.1% of never vs 20.3% of ever users had a hysterectomy. Adjustment for this modest difference made no difference to endometrial cancer risk. There would have to be a substantial difference between groups in hysterectomy rates after leaving GP observation to explain our observed 34% reduction in endometrial cancer risk in ever users. We have reported a 50% higher usage of HT in past users of OCs who have not had a hysterectomy than similar never users.2Moorhead T. Hannaford P. Warskyj M. Prevalence and characteristics associated with use of hormone replacement therapy in Britain.BJOG. 1997; 104: 290-297Crossref Scopus (71) Google Scholar Others have found that HT may increase the risk of ovarian cancer.3Collaborative Group on Epidemiological Studies of Ovarian CancerMenopausal hormone use and ovarian cancer risk: individual participant meta-analysis of 52 epidemiological studies.Lancet. 2015; 385: 1835-1842Abstract Full Text Full Text PDF PubMed Scopus (271) Google Scholar Failure to adjust for possible higher HT usage by previous OC users would diminish, not increase, differences in ovarian cancer risk between ever and never OC users. Our results provide robust evidence that most OCs users do not expose themselves to long-term cancer harms. Lifetime cancer risk with progestin and estrogen oral contraceptives and hormone therapyAmerican Journal of Obstetrics & GynecologyVol. 217Issue 2PreviewThe Royal College of General Practitioners’ Oral Contraception (OC) Study authors claim ever use gives long-term reductions in the risk of some cancers.1 Progestins and estrogens are highest level carcinogens. The study previously found increases in breast cancers (×2.81 at age 15-29 years and ×3.33 at age 30-34 years), cervical cancers (×2.75), and central nervous system or pituitary tumors (×5.51) with >8 years of OC use; ≥10 years of use increased mortality from cervical cancers (×4.1) and lung cancers (×2). Full-Text PDF